The present invention relates to a six degrees-of-freedom tracking system by which spatial information, including the location (X,Y,Z) and orientation (roll, pitch, yaw) about an object in space (for example a robot arm, platform, or a helmet in an aircraft) can be accurately determined by electro-optical means. The invention has application either in open-loop position locating systems or in closed-loop control systems.
Prior Art systems include, among others, those shown in U.S. Pat. No. 4,396,945, entitled "Method of Sensing the Position and Orientation of Elements in Space" issued to Paul DiMatteo, et al and U.S. Pat. No. 4,238,828, entitled "Position Detecting Apparatus" issued to Andrew G. Hay, et al. The systems described in the above referred to patents include a plurality of target spots or points in fixed relationship to an object whose position is to be monitored. One or more cameras, having a field of view of the target spots, are provided to obtain a projection of the target points on one or more two dimensional image planes. Means are provided to generate signals representative of the two dimensional position coordinates of the image points on the image planes corresponding to the target points. From the position coordinate information of the image points corresponding to the target points, an analytical processor provides spatial information about the object relative to the image plane coordinate frame.
The arrangement of the target spots determines in part the mathematical processes to obtain position information. Heretofore, prior art systems include the solution of a plurality of simultaneous equations usually in quadratic or higher order forms. The four non-coplanar point array shown in U.S. Pat. No. 4,238,828, is computationally cumbersome since six quadratic simultaneous equations must be solved to obtain a solution. Still, in other solutions, a simultaneous set of quadratic equations must be solved. Accordingly, processer times and complexity of the processer increases with such solutions.